Lactoferrin-induced apoptosis and PLD activation in oral squamous cell carcinoma cell line

在本研究中，我研究胃蛋白酶水解乳铁蛋白（乳铁蛋白）诱导口腔鳞状细胞癌细胞株凋亡的生物学机制。[结果]胃蛋白酶消化的乳铁蛋白处理口腔癌细胞引起以下变化：1）抑制|3H| 2）Hoechst 33258染色的染色质的诱导浓缩。3）诱导DNA的断裂。4）增加细胞内LDH的泄漏。5）增加ERK蛋白磷酸化（=激活）。6）延长血清诱导ERK、JNK蛋白磷酸化。7）刺激PLD激活。8）抑制PKC ε和η同工酶mRNA表达。我们发现，由牛乳铁蛋白的酸性胃蛋白酶水解产生的乳铁蛋白肽诱导涉及人口腔鳞状细胞癌细胞系中的凋亡性核变化的细胞死亡。在细胞凋亡的早期阶段，乳铁素处理诱导ERK和PLD的激活，并延长血清诱导的ERK和JNK的激活在后期（24-27小时）。此外，乳铁蛋白肽处理6小时降低蛋白激酶Cε和η同工酶的mRNA表达水平。这些信号酶的变化可能在乳铁蛋白肽诱导口腔癌细胞凋亡过程中发挥作用。

In the present study, I examined biological mechanisms of apoptosis induced by pepsin hydrolyzed-lactoferrin (lactoferricin) in oral squamous cell carcinoma cell lines.【RESULTS】The treatment of oral cancer cells with pepsin-digested lactoferrin caused changes as followed.1) Suppressed |3H|thymidine incorporation.2) Induced condensation of chromatin stained by Hoechst 33258.3) Induced the fragmentation of DNA.4) Increased the leak of intracellular LDH.5) Increased ERK protein phosphorylation (=activations).6) Elongated serum-induced ERK, JNK protein phosphorylation.7) Stimulated PLD activation.8) Suppressed mRNA expression of PKC ε and η isozymes【Conclusion】In this study, we found that lactoferricin peptides, produced by acid-pepsin hydrolysis of bovine lactoferrin, induced cell death involving apoptotic nuclear change in human oral squamous cell carcinoma cell lines. At early stage of apoptosis, the treatment of lactoferricin induced activations of ERK, and PLD and prolonged serum-induced activations of ERK and JNK at later stage (24-27 hrs). Moreover, 6hrs treatment of lactoferricin peptides decreased mRNA expression levels of protein kinase Cε and η isozymes. These changes of signaling enzymes may play a role in apoptotic process of oral cancer cells induced by lactoferricin peptides.